Micro fractures ... fact or fiction?

[austinconrad]

I have alway heard people telling me that if you drop a carabiner or metal piece of gear onto a hard surface it must always be retired no questions asked. I never really cared that much because I figured I would just never drop any gear off a route. Well today I dropped two carabiners from the top of the slabs and they bounced of a couple ledges pretty hard before hitting the ground. I went online and found conflicting opinions on wether micro fractures actually existed including one from BD that basically said micro fractures are not as big of a deal as people make them out to be (but of course adding that if in doubt it should be replaced). I'm probably going to end up replacing them because I'm uncertain but I was wondering if any one has an interesting opinion/story on this.

Thanks

[chossmonkey]

If there are any big gouges or deformations retire the biners. If they are just scuffed I wouldn't worry about it.

If you aren't quite sure if you should trash or save, then hold onto them and use them as bail biners.

[betaburgler]

First I think perhaps what people are referring to when they say "micro-fractures" is unseen internal damage. If you drop an aluminum biner you will likely see the damage at the surface. Dents, deformation and visible cracking might make any sane person retire a piece of equipment that they will be relying on for life and limb. Well unless you're a mankey smelly climbing bum, than it is just a "motivational aid".

What you might not see is how the micro-structure has been affected when there is no major visible damage (generally not much, but some things are difficult to predict). I think the larger danger is if you than use that biner and fall on it repeatedly. Internal damage from a drop might provide a flaw for the initiation of a fatigue crack. Fatigue cracks grow over time, a little bit with every application of stress. They are inherently dangerous because you might not see a fatigue crack before it weakens the biner enough that it fails.

Personally I like Chossmonkey's take on it, but ultimately everyone has to add the old when in doubt don't so that they don't get sued if you make a bad decision. So when in doubt don't use it